A variety of products are now commonly packaged in reclosable plastic containers with the expectation that the consumer will retain the container for a period of time to store the purchased articles. Consequently, such containers must be capable of withstanding a reasonable number of cycles of opening and closing during the expected period of use of the articles. The functioning of the container, particularly the ease by which the container may be closed and reopened, thus becomes an important factor in total consumer satisfaction.
A typical plastic container intended to hold merchandise at the point of sale has a bottom portion or base and a top lid or cover attached to the base by a hinge. Although rectangular packages are most common, the base and cover may have a variety of configurations, including polygonal, round, oblong, etc. To hold the cover to the base when the cover is closed, it is very common to provide some means for interlocking the cover and base. One type of interlocking structure is obtained by providing an upstanding shoulder about the periphery of the base which has an outwardly extending, overhanging lip. The cover has a depending wall portion with an indentation therein adapted to mate with the lip on the base so that, when the cover is pressed to the base, the indentation and lip engage with each other in a "snap" fit. The engagement between the lip and indentation holds the cover and base together during normal handling, but allows them to be parted when sufficient force pulling them apart is exerted.
For many containers having a secure snap fit closure, it may be very difficult or inconvenient for the user to reopen the container simply by grabbing the two halfs and pulling them apart. For example, the base and cover portions may not be readily grasped by the hands of the user; the base and cover may be too large or too small or too slippery or in a shape which is difficult to hold. Under some circumstances, it may be desirable or even necessary that the user be able to open the container using only one hand, such as where the container is intended to be used by the elderly or disabled. Consequently, many of the presently available reclosable containers have some feature formed on them specifically intended to aid the user in reopening the container. For example, it is common for containers to be provided with flanges which extend outwardly from the peripheries of the base and cover portions; usually, the flanges are formed adjacent to one another but do not entirely overlap. The user then may pull the flange portions on the cover and base away from each other with his fingers to draw the cover and base apart. The finger manipulation required to pull such flanges apart can present problems to some users, such as those afflicted with arthritis. In addition, many containers have snap fit interlocks at more than one position on the containers, such as each of the two free (unhinged) corners of a rectangular container, such that two sets of opening aid flanges must be provided with one set of flanges adjacent to each of the interlocking positions. The opening force applied at the position of one of the interlocks may not sufficiently part the cover and base to release the interlock which is not adjacent, thus requiring that the user use both hands to open the container at the two sets of flanges.